Reverse Micelles for Nanoparticle Synthesis and Biomolecule Separation. In: Ranjan S, Dasgupta N, Lichtfouse E, editors. Nanoscience in Food and Agriculture 4. Cham: Springer International Publishing; 2017. pp. 181-211. [DOI: 10.1007/978-3-319-53112-0_5]

Green and sensitive detection of olopatadine in aqueous humor using a signal-on fluorimetric approach: GREEnness assessment

Olopatadine (OLP) is widely utilized as an effective antihistaminic drug for alleviating ocular itching associated with allergic conjunctivitis. With its frequent usage in pharmacies, there arises a pressing need for a cost-effective, easily implementable, environmentally sustainable detection method with high sensitivity. This study presents a novel signal-on fluorimetric method for detecting OLP in both its pure form and aqueous humor. The proposed approach depends on enhancing the weak intrinsic fluorescence emission of OLP, achieving a remarkable increase of up to 680% compared to its intrinsic fluorescence. This enhancement is achieved by forming micelles around protonated OLP using an acetate buffer (pH 3.6) and incorporating a solution of sodium dodecyl sulfate (SDS) surfactant. A strong correlation (R = 0.9996) is observed between the concentration of OLP and fluorescence intensities ranging from 1.0 to 100.0 ng mL-1 with a limit of detection of 0.22 ng mL-1. This described method is successfully employed for quantifying OLP in both its powder form and pharmaceutical eye drops. Furthermore, it demonstrates robust performance in determining OLP in artificial aqueous humor with a percentage recovery of 99.05 ± 1.51, with minimal interference from matrix interferents. Moreover, the greenness of the described method was evaluated.

Self-Emulsifying Drug Delivery Systems (SEDDS) Containing Reverse Micelles: Advanced Oral Formulations for Therapeutic Peptides

Alternative methods to hydrophobic ion pairing for the formation of lipophilic complexes of peptide drugs to incorporate them in lipid-based nanocarriers such as self-emulsifying drug delivery systems (SEDDS) for oral administration are highly on demand. Such an alternative might be reverse micelles. Within this study, SEDDS containing dry reverse micelles (dRMsPMB ) formed with an anionic (sodium docusate; AOT), cationic (dimethyl-dioctadecyl-ammonium bromide; DODAB), amphoteric (soy lecithin; SL), or non-ionic (polysorbate 85; P85) surfactant loaded with the model peptide drug polymyxin B (PMB) are developed. They are characterized regarding size, payload, release kinetics, cellular uptake, and peptide activity. SEDDS exhibit sizes from 22.2 ± 1.7 (AOT-SEDDS-dRMsPMB ) to 61.7 ± 3.2 nm (P85-SEDDS-dRMsPMB ) with payloads up to 2% that are approximately sevenfold higher than those obtained via hydrophobic ion pairing. Within 6 h P85-SEDDS-dRMsPMB and AOT-SEDDS-dRMsPMB show no release of PMB in aqueous medium, whereas DODAB-SEDDS-dRMsPMB and SL-SEDDS-dRMsPMB show a sustained release. DODAB-SEDDS-dRMsPMB improves uptake by Caco-2 cells most efficiently reaching even ≈100% within 4 h followed by AOT-SEDDS-dRMsPMB with ≈20% and P85-/SL-SEDDS-dRMsPMB with ≈5%. The peptide drug maintains its antimicrobial activity in all SEDDS-dRMsPMB . According to these results, SEDDS containing dRMs might be a game changing strategy for oral peptide drug delivery.

Bioremediation of phenolic pollutant bisphenol A using optimized reverse micelles system of Trametes versicolor laccase in non-aqueous environment

In recent times, there is increased public interest and indeed strong movement against the use of Bisphenol A (4,4'-(propane-2,2,-diphenol)) due to its endocrine disrupting properties. In the present study, biotransformation of Bisphenol A (BPA) was accomplished using Trametes versicolor laccase (E.C. 1.10.3.2) enzyme. The enzyme was entrapped in reverse micelles comprising of bis(2-ethylhexyl) sulfosuccinate sodium salt (AOT) and 2,2,4-trimethylpentane (isooctane) for non-aqueous catalysis considering hydrophobicity of BPA. Screening of various parameters that may affect micellar system was carried out using Plackett-Burman experimental design and central composite design (Design Expert 11). According to Design Expert actual concentration of different variables was 0.55, 150 (Wo 30), 0.0035 mM and 175 µg/ml for Mg⁺²ions, Hydration ratio (Wo), 2,6-dimethoxyphenol (2,6 DMP, substrate) and laccase, respectively, at 40 °C and pH 4.5. Under these conditions laccase activity in reverse micelles was increased two folds as compared to unoptimized micellar system. It was evident that the reverse micelles diameter was linearly proportionated to the amount of laccase enzyme incorporated. BPA bioremediation mediated by laccase in non-aqueous environment was found to be 84% in 8 h of treatment. Biotransformation of BPA was monitored using GC-MS. BPA degraded products, such as BPA-O-catechol and 4,4 (Ethane 2-oxy 2-ol) diphenol were identified indicating transformation by oxidation.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-021-02842-4.

Predicting the size of salt-containing aqueous Na-AOT reverse micellar water-in-oil microemulsions with consideration for specific ion effects

HYPOTHESIS

Reverse micellar solutions are thermodynamically stable systems in which surfactant molecules surround water droplets within a continuous organic phase. Among their many applications, they can be used for the synthesis of nanoparticles of controlled agglomeration. Here, we consider the role specific ion effects play in reverse micelle size reduction.

EXPERIMENTS

Dynamic light scattering measurements and the Gouy-Chapman electrical double layer model were combined to study water/AOT/isooctane reverse micellar systems (w_o = 10). Linear relationships between the solvodynamic diameter (D) of reverse micelles containing various concentrations of FeSO₄, Mg(NO₃)₂, CuCl₂, Al(NO₃)₃, Fe(NO₃)₃, Y(NO₃)₃, NaBH₄, ZrOCl₂, and NH₄OH, and their calculated Debye screening lengths, κ^-1, were observed with decreasing D and increasing salt concentration (c).

FINDINGS

By comparing the linear fits for reverse micelle size as a function of c^-1/2, we determined the size can be described as a function of the Debye screening length, cation valency (z), and specific anion hydrated radius (r_an), where D = 3.1z κ^-1 + b_i, and b_i is linearly related to r_an. Our model accurately predicts reverse micelle sizes with the addition of monovalent, divalent, and trivalent salts for which the primary hydrolyzed cation species has a charge that is equal to the cation valency.

Versatility of Reverse Micelles: From Biomimetic Models to Nano (Bio)Sensor Design

This paper presents an overview of the principal structural and dynamics characteristics of reverse micelles (RMs) in order to highlight their structural flexibility and versatility, along with the possibility to modulate their parameters in a controlled manner. The multifunctionality in a large range of different scientific fields is exemplified in two distinct directions: a theoretical model for mimicry of the biological microenvironment and practical application in the field of nanotechnology and nano-based sensors. RMs represent a convenient experimental approach that limits the drawbacks of the conventionally biological studies in vitro, while the particular structure confers them the status of simplified mimics of cells by reproducing a complex supramolecular organization in an artificial system. The biological relevance of RMs is discussed in some particular cases referring to confinement and a crowded environment, as well as the molecular dynamics of water and a cell membrane structure. The use of RMs in a range of applications seems to be more promising due to their structural and compositional flexibility, high efficiency, and selectivity. Advances in nanotechnology are based on developing new methods of nanomaterial synthesis and deposition. This review highlights the advantages of using RMs in the synthesis of nanoparticles with specific properties and in nano (bio)sensor design.

Extraction and reimmobilization of used commercial lipase from industrial waste

In industrial application, immobilized lipase are typically not reused and served as industrial waste after a certain process is completed. The capacity on the reusability of the spent lipase is not well studied. This current study embarks on reusing the remaining lipase from the spent immobilized enzyme. Active lipases were recovered using a simple reverse micellar extraction (RME). RME is the extraction process of targeted biomolecules using an organic solvent and a surfactant. This method was the first attempt reported on the recovery of the lipase from the used immobilized lipase. RME of the spent lipase was done using the nonionic Triton X-100 surfactant and toluene. Various parameters were optimized to maximize the lipase recovery from the used immobilized lipase. The optimum forward extraction condition was 0.075 M KCl, and backward conditions were at 0.15 M Triton X-100/toluene (pH 6, 2 M KCl) with recovery of 66%. The extracted lipase was immobilized via simple adsorption into the ethanol pretreated carrier. The optimum conditions of immobilization resulted in 96% of the extracted lipase was reimmobilized. The reimmobilized lipase was incubated for 20 h in pH 6 buffer at 50 °C of water bath shaker. The reimmobilized lipase still had 27% residual activity after 18 h of incubation, which higher thermal stability compared to the free lipase. In conclusion, the free lipase was successfully extracted from the spent immobilized lipase and reimmobilized into the new support. It exhibited high thermal stability, and the reusability of the spent lipase will promote continued use of industrial lipase and reduce the cost of the manufacturing process.

Hybrid Atomistic and Coarse-Grained Model for Surfactants in Apolar Solvents

Here, we develop and verify the performance of a hybrid molecular modeling approach that combines coarse-grained apolar solvent and atomistic solute or polar solvent description, for example, for description of reverse micellar systems. The coarse-grained solvent model is directly applicable to organic solvents encompassing alkane, alkene, and fatty acid ester functional groups and connects directly to both standard united-atom GROMOS 53A6 and all-atom CHARMM27 force fields, as well as the atomistic detail water models compatible with these force fields. The different levels of description are coupled via explicit, unscaled electrostatics, and scaled mixing rules for dispersive interactions. The hybrid model is in near-quantitative agreement with fully atomistic simulations when combined with the CHARMM27 model but underestimates modestly surfactant aggregation when using GROMOS 53A6 united-atom description. The use of truncated electrostatics affords up to a 9-fold increase in computational speed without significant loss of accuracy. However, long-range electrostatic calculations and load imbalance at high core counts can significantly degrade the performance. We demonstrate the usability of the hybrid model by assessing the reverse micelle formation of a homologous series of nonionic glycerolipids via large-scale self-assembly simulations. The presented model is demonstrated here for accurate description of surfactant systems in apolar solvents, with and without also polar solvent (water) in the system. The formulation can be expected to describe well also other solute species or interfaces with an apolar solvent in an apolar environment.

Catanionic Reverse Micelles as an Optimal Microenvironment To Alter the Water Electron Donor Capacity in a SN2 Reaction

The effect of interfacial water entrapped in two types of catanionic reverse micelles (RMs) on the kinetic parameters of the S_N2 reaction between dimethyl-4-nitrophenylsulfonium trifluoromethanesulfonate (S⁺) and n-butylamine (BuNH₂) was explored. Two catanionic surfactants, composed of a mixture of oppositely charged ionic surfactants without their original counterions, were used to create the RMs. Thus, benzyl- n-hexadecyldimethylammonium 1,4-bis(2-ethylhexyl) sulfosuccinate (BHD-AOT) and cetyltrimethylammonium 1,4-bis(2-ethylhexyl) sulfosuccinate (CTA-AOT) were formed. Also, the well-known anionic surfactant sodium 1,4-bis(2-ethylhexyl) sulfosuccinate (Na-AOT) was employed as a comparison. Our results showed an important catalytic-like effect of all RMs investigated in comparison with a water-benzene mixture, and the rate constant values depend on the type of surfactant used. Faster reaction in BHD-AOT RMs than in CTA-AOT and Na-AOT RMs was observed. This behavior was attributed to the strong interaction (by hydrogen bonding with AOT anion and ion-dipole interaction with BHD⁺) between the entrapped water and the BHD-AOT interface, which reduces the solvation capacity of water on S⁺. In CTA-AOT (and Na-AOT) RMs, the water-interface interaction is weaker and the electron pairs of water can solvate S⁺ ions. In summary, the chemical structure of the counterion on the catanionic surfactant alters the interfacial region, allowing the progress of a reaction inside the RMs to be controlled.